DIN2630, DIN2631, DIN2632, DIN2633, DIN2634, DIN2635, DIN2636, DIN2637 Welding Neck Flanges (PN1-PN100)

Welding Neck Flanges is the correct terminology to be used as per ASME B31.3 and ASME B16.5. However in the industry welding neck flanges are commonly referred to as weld neck flanges or WN flanges. The Welding Neck Flange consists of a tapered hub which is secured to the pipe by a full penetration butt weld. Because of the additional reinforcement area available in the hub of weld neck flange and due to its installation by welding, the hub becomes an integral part of the pipe. This gives a weld neck flange greater strength and integrity and ability to withstand considerably higher bending moments than a slip-on flange. Since weld neck flanges are secured to pipe by butt-welding, the internal diameter of the hub end should match the internal diameter of the pipe end. The details of matching pipe ID or wall thickness are required to be specified for purchasing weld neck flanges.

Advantages of Welding Neck Flanges
Following are the advantages of weld neck flanges:

• The butt-weld permits non-destructive examination by radiography to be carried out on the weld neck flange unlike slip-on flange which can be examined only by magnetic particle inspection or dye penetration inspection
• The weld neck flange can be directly welded to butt-weld fittings like elbows, tees or reducers without requiring any short piece of pipe unlike slip-on flange which require a straight length of pipe for installation
• Despite the initial procurement cost of weld neck flange being higher than a slip-on flange, the installation cost (which includes welding and inspection) reduces the differential
• Welding neck flanges can withstand higher bending moments
• Welding neck flanges are suitable for piping systems subject to high pressures, high cyclical loading, high temperatures as well as cryogenic services